Multi-layer cast film

ABSTRACT

A multi-layer polymer film comprising a core layer and a sealing layer, 
     said sealing layer comprises a propylene copolymer composition, said propylene copolymer composition 
     
         
         
           
             has a comonomer content in the range of 3.0 to 8.0 wt.-%, the comonomers are C 5  to C 12  α-olefins, 
             comprises a polypropylene (A) and a polypropylene (B) in the weight ratio [(A)/(B)] of 20/80 to 80/20, 
             wherein 
             said polypropylene (A) has a comonomer content of equal or below 4.0 wt.-%, the comonomers are C 5  to C 12  α-olefins, and 
             said propylene copolymer (B) has a comonomer content of 4.0 to 20.0 wt.-%, the comonomers are C 5  to C 12  α-olefins.

The present invention is directed to a new unoriented multi-layerpolymer film comprising a sealing layer with good optical and sealingproperties, as well as to its manufacture.

Polypropylenes are suitable for many applications. For instancepolypropylene is applicable in areas where sealing properties play animportant role, like in the food packing industry. Irrespectively fromthe polymer type, a polymer must fulfill at best all desired endproperties and additionally must be easily processable, i.e. mustwithstand stress. However end properties and processing properties actoften in a conflicting manner.

In many cases, the seal which is formed between the surfaces to besealed is put under load while it is still warm. This means that thehot-tack properties of the polypropylene are crucial to ensure that astrong seal is formed even before cooling. But not only the hot tackstrength should be rather high but also the heat sealing initiationtemperature should be rather low. By operating at lower temperaturethere is the benefit that the article to be sealed is not exposed tohigh temperature. There are also economic advantages since lowertemperatures are of course cheaper to generate and maintain. Further,all extrusion products have a window within which sealing may occur,i.e. in which the sealing layer becomes partly molten. Traditionallythis sealing window has been rather narrow meaning that temperaturecontrol during the heat sealing process is critical. Accordingly a broadsealing window would be appreciated because in such a case thetemperature control during heat sealing is less important.

Additionally the melting temperature of the used polypropylene should berather high to avoid stickiness and blocking during the manufacture ofthe film material.

Finally for many applications the film material shall also have goodoptical properties.

Accordingly the object of the present invention is to provide a materialenabling a skilled person to produce a multi-layer polymer film havinghigh hot tack strength, low heat sealing initiation temperature (SIT),broad processing window, low stickiness and good optical properties.

The finding of the present invention is to provide a multi-layer filmcomprising a core layer (CL) and sealing layer (SL) comprising apropylene copolymer composition (P) with rather high comonomer content,the comonomers are long chain α-olefins, and said propylene copolymercomposition (P) comprises two different fractions, said fractions differin the comonomer content.

Accordingly in a first embodiment the present invention is directed to amulti-layer polymer film, preferably is directed to an unorientedmulti-layer polymer film, comprising

-   (a) a core layer (CL) being selected from the group consisting of    polyvinyl alcohols, polyacrylates, polyamides, poly(ethylene    terephthalate), polyolefins (PO) and mixtures thereof, and-   (b) a sealing layer (SL),    said sealing layer (SL) comprises a propylene copolymer composition    (P), said propylene copolymer composition (P)-   (c1) has a comonomer content in the range of 3.0 to 8.0 wt.-%, the    comonomers are C₅ to C₁₂ α-olefins,-   (c2) comprises a polypropylene (A) and a polypropylene (B) in the    weight ratio [(A)/(B)] of 20/80 to 80/20, preferably of 25/75 to    75/25, more preferably of 30/70 to 70/30, still more preferably of    35/65 to 50/50,    wherein    -   said polypropylene (A) has a comonomer content of equal or below        4.0 wt.-%, the comonomers are C₅ to C₁₂ α-olefins, and    -   said propylene copolymer (B) has a comonomer content of 4.0 to        20.0 wt.-%, the comonomers are C₅ to C₁₂ α-olefins.

Alternatively (second embodiment) the present invention can be definedas a multi-layer polymer film, preferably as an unoriented multi-layerpolymer film, comprising

-   (a) a core layer (CL) being selected from the group consisting of    polyvinyl alcohols, polyacrylates, polyamides, poly(ethylene    terephthalate), polyolefins (PO) and mixtures thereof, and-   (b) a sealing layer (SL),    said sealing layer (SL) comprises a propylene copolymer composition    (P), said propylene copolymer composition (P) has-   (c1) a comonomer content in the range of 3.0 to 8.0 wt.-%, the    comonomers are C₅ to C₁₂ α-olefins,-   (c2) a melting temperature Tm determined by differential scanning    calorimetry (DSC) of at least 135° C., and-   (c3) a heat sealing initiation temperature (SIT) of equal or below    112° C., preferably of equal or below 110° C.

The term “unoriented” shall indicated that the multi-layer polymer filmis not dimensionally stretched as this is the case for biaxiallyoriented films or blown films. Accordingly it is preferred that themulti-layer polymer film, i.e. the polymer layers of the multi-layerpolymer film, is (are) not biaxially stretched or uniaxially stretched.Accordingly it is appreciated that that the multi-layer polymer film isunstretched. Accordingly it is in particular preferred that all polymerlayers of the multi-layer polymer film are extruded on a cast film line.Thus in one specific aspect the present invention is directed tomulti-layer polymer cast film, i.e. to an unoriented multi-layer polymercast film.

It has surprisingly been found that such a multi-layer polymer film hasa low heat sealing initiation temperature (SIT), a broad sealing window,a high hot tack strength and good optical properties (see examplesection).

In the following the invention is defined in more detail.

The multi-layer polymer film according to the instant inventioncomprises a core layer (CL) and at least one sealing layer (SL).Accordingly the multi-layer polymer film may comprise additional layerslike an outer layer (OL) and/or a metal layer (ML). The metal layer (ML)is applied after the polymer layers, in particular the core layer (CL),the sealing layers (SL) and optionally the outer layer (OL) have beenextruded.

In one preferred embodiment the multi-layer polymer film comprises atleast three layers, namely at least one core layer (CL), and two sealinglayers (SL), namely a first sealing layer (SL) and a second sealinglayer (SL), wherein the multi-layer polymer film has the stacking orderfirst sealing layer (SL)-core layer (CL)-second sealing layer (SL).Accordingly in one preferred embodiment the (two) sealing layer(s) aredirectly co-extruded with the core layer (CL). Thus in one specificpreferred embodiment multi-layer polymer film consists of two sealinglayers (SL) and one core layer (CL) having the stacking order firstsealing layer (SL)-core layer (CL)-second sealing layer (SL). The firstsealing layer (SL) and second sealing layer (SL) can be chemicallydifferent or identical. In one embodiment the first sealing layer (SL)and second sealing layer (SL) are chemically identical.

In another preferred embodiment the multi-layer polymer film comprisesat least three layers, namely a core layer (CL), a sealing layer (SL)and a metal layer (ML), wherein the sealing layer (SL) is located, i.e.joined, on the one side (surface) of the core layer (CL) and the metallayer (ML) is located, i.e. joined, on the other side (surface) of thecore layer (CL). Accordingly the multi-layer polymer film has thestacking order sealing layer (SL)-core layer (CL)-metal layer (ML).Preferably the sealing layer (SL) is co-extruded with the core layer(CL), and subsequently the core layer (CL) is metallized obtaining themetal layer (ML).

In another preferred embodiment the multi-layer polymer film comprisesat least three layers, namely a core layer (CL), a sealing layer (SL)and a outer layer (OL), wherein the sealing layer (SL) is located, i.e.joined, on the one side (surface) of the core layer (CL) and the outerlayer (OL) is located, i.e. joined, on the other side (surface) of thecore layer (CL). Accordingly the multi-layer polymer film has thestacking order sealing layer (SL)-core layer (CL)-outer layer (OL).Preferably the sealing layer (SL) and the outer layer (OL) areco-extruded with the core layer (CL).

The thickness of the core layer (CL) is preferably in the range of 5 to500 μm, more preferably in the range of 20 to 100 μm.

Preferably the sealing layer(s) (SL) has/have a thickness that issubstantially less than the thickness of the core layer (CL) andsubstantially less than the thickness of the total multi-layer polymerfilm. In one embodiment the thickness of the sealing layer(s) (SL)is/are substantially less, usually less than 20%, of the thickness ofthe core layer (CL). Accordingly it is appreciated that the sealinglayer(s) (SL) has/have a thickness in the range of 0.5 to 30 μm, morepreferably in the range of 2 to 15 μm.

The outer layer (OL)—if present—may have a thickness in the range of 2to 50 μm, more preferably in the range of 2 to 20 μm.

Preferably the multi-layer polymer film is obtained by coextrusion. Theextrusion coating can be accomplished on a cast film line. An especiallypreferred process for the preparation of a multi-layer film according tothis invention is described in more detail below.

As used herein, the phrase “core layer” although singular, may refer toone or more layers, like to 2 to 5 layers, i.e. 2, 3, 4, or 5 layers,that form the core of the multi-layer polymer film. The core layer (CL)will typically be formed from a polymer selected from the groupconsisting of polyvinyl alcohol, polyacrylate, polyamide, polyester,like poly(ethylene terephthalate), polyolefin (PO) and mixtures thereofhaving desired properties or characteristics, such as good stiffness orbarrier properties. Accordingly it is in particular preferred that thecore layer (CL) is a polyolefin (PO), more preferably a polyethylene(PE) or polypropylene (PP), still more preferably a propylene copolymer(C-PP) or a propylene homopolymer (H-PP), the latter being preferred. Incase of a propylene copolymer, said copolymer has preferably a comonomercontent between 0.1 and 5 wt.-%, the comonomers are ethylene and/or C₄to C₈ α-olefins, preferably ethylene, 1-butene or 1-hexene.

In one preferred embodiment the polypropylene (PP), preferably thepropylene homopolymer (H-PP), of the core layer (CL) has a melt flowrate MFR₂ (230° C.) measured according to ISO 1133 in the range of 1.0to 15.0 g/10 min, more preferably in the range of 1.0 to 10.0 g/10 min.

The melting temperature Tm determined by differential scanningcalorimetry (DSC) of the polypropylene (PP), more preferably of thepropylene homopolymer (H-PP), is at least 150° C., preferably at least155° C., more preferably in the range of 150 to 166° C., like in therange of 160 to 164° C.

The outer layer (OL)—if present—is preferably a polyolefin (PO) Thepolyolefin (PO) of the outer layer (OL) can be identical or different tothe polyolefin (PO) of the core layer (CL). Accordingly with regard tothe preferred polyolefin (PO) used as the outer layer (OL) reference ismade to the information provided above for the polyolefin (PO) used asthe core layer (CL). In one embodiment the outer layer (OL) is apolyamide, a polyester, a polyvinyl alcohol, a polyethylene (PE) or apolypropylene (PP).

In one embodiment the polyolefin (PO) of the core layer (CL) and outerlayer (OL) are identical, more preferably a propylene homopolymer (H-PP)as defined above.

As a further requirement the sealing layer(s) (SL) of the multi-layerpolymer film must comprise a propylene copolymer composition (P). In apreferred embodiment the sealing layer(s) (SL) comprise(s) the propylenecopolymer composition (P) as the only polymer component. Accordingly itis preferred that the amount of the propylene copolymer composition (P)within the sealing layer(s) (SL) is at least 70 wt.-%, more preferablyat least 80 wt.-%, still more preferably at least 90 wt.-%, still yetmore preferably at least 95 wt.-%, like at least 99 wt.-%. In onepreferred embodiment the sealing layer(s) (SL) consist(s) of thepropylene copolymer composition (P).

The propylene copolymer composition (P) according to this invention isfeatured by a rather high comonomer content. A “comonomer” according tothis invention is a polymerizable unit different to propylene.Accordingly the propylene copolymer composition (P) according to thisinvention shall have a comonomer content of at least 2.5 wt.-%, morepreferably of at least 3.0 wt.-%, more preferably of at least 3.3 wt.-%,still more preferably of at least 3.5 wt.-%, like of at least 3.8 wt.-%.Thus it is preferred that the propylene copolymer composition (P)according to this invention has a comonomer content in the range of 2.0to 10.0 wt.-%, more preferably in the range of 3.0 to 8.0 wt.-%, stillmore preferably in the range of 3.2 to 7.5 wt.-%, still more preferablyin the range of 3.3 to 7.5 wt.-%, like in the range of 3.5 to 6.5 wt.-%.

In a preferred embodiment the amount of comonomer within the sealinglayer(s) (SL) is the same as for the propylene copolymer composition(P).

The comonomers of the propylene copolymer composition (P) are C₅ to C₁₂α-olefins, e.g. 1-hexene and/or 1-octene. The propylene copolymercomposition (P) of the present invention may contain more than one typeof comonomer. Thus the propylene copolymer composition (P) of thepresent invention may contain one, two or three different comonomers,the comonomers are selected from the group of C₅ α-olefin, C₆ α-olefin,C₇ α-olefin, C₈ α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, andC₁₂ α-olefin. However it is preferred that the propylene copolymercomposition (P) contains only one type of comonomer. Preferably thepropylene copolymer composition (P) comprises—apart from propylene—only1-hexene and/or 1-octene. In an especially preferred embodiment thecomonomer of the propylene copolymer composition (P) is only 1-hexene.

The propylene copolymer composition (P) as well as the propylenecopolymer (B) and the propylene copolymer (C-A) according to thisinvention are preferably random propylene copolymers. The term “randomcopolymer” has to be preferably understood according to IUPAC (PureAppl. Chem., Vol. No. 68, 8, pp. 1591 to 1595, 1996). Preferably themolar concentration of comonomer dyads, like 1-hexene dyads, obeys therelationship[HH]<[H]²wherein

-   [HH] is the molar fraction of adjacent comonomer units, like of    adjacent 1-hexene units, and-   [H] is the molar fraction of total comonomer units, like of total    1-hexene units, in the polymer.

Preferably the propylene copolymer composition (P) as well as thepropylene copolymer (C-A) and the propylene copolymer (B) as defined indetail below are isotactic. Accordingly it is appreciated that thepropylene copolymer composition (P), the propylene copolymer (C-A) andthe propylene copolymer (B) have a rather high isotactic triadconcentration, i.e. higher than 90%, more preferably higher than 92%,still more preferably higher than 93% and yet more preferably higherthan 95%, like higher than 97%.

The molecular weight distribution (MWD) is the relation between thenumbers of molecules in a polymer and the individual chain length. Themolecular weight distribution (MWD) is expressed as the ratio of weightaverage molecular weight (M_(w)) and number average molecular weight(M_(n)). The number average molecular weight (M_(n)) is an averagemolecular weight of a polymer expressed as the first moment of a plot ofthe number of molecules in each molecular weight range against themolecular weight. In effect, this is the total molecular weight of allmolecules divided by the number of molecules. In turn, the weightaverage molecular weight (M_(w)) is the first moment of a plot of theweight of polymer in each molecular weight range against molecularweight.

The number average molecular weight (M_(n)) and the weight averagemolecular weight (M_(w)) as well as the molecular weight distribution(MWD) are determined by size exclusion chromatography (SEC) using WatersAlliance GPCV 2000 instrument with online viscometer. The oventemperature is 140° C. Trichlorobenzene is used as a solvent (ISO16014).

Accordingly it is preferred that the inventive propylene copolymercomposition (P) has a weight average molecular weight (M_(w)) from 100to 700 kg/mol, more preferably from 150 to 400 kg/mol.

The number average molecular weight (M_(n)) of the polypropylene ispreferably in the range of 25 to 200 kg/mol, more preferably from 30 to150 kg/mol.

Further it is appreciated that the molecular weight distribution (MWD)measured according to ISO 16014 is at least 2.5, preferably at least 3,more preferably in the range of 2.5 to 8, more preferably 3 to 5.

Furthermore, it is preferred that the propylene copolymer composition(P) of the present invention has a melt flow rate (MFR) given in aspecific range. The melt flow rate measured under a load of 2.16 kg at230° C. (ISO 1133) is denoted as MFR₂. Accordingly, it is preferred thatin the present invention the propylene copolymer composition (P) has amelt flow rate MFR₂ measured according to ISO 1133 in the range of 2.0to 50.0 g/10 min, more preferably in the range of 3.0 to 25.0 g/10 min,still more preferably in the range of 3.0 to 20.0 g/10 min, yet stillmore preferably in the range of 4.0 to 15.0 g/10 min.

In a preferred embodiment the molecular weight distribution (MWD), theweight average molecular weight (M_(w)), the number average molecularweight (M_(n)) and the melt flow rate (MFR) of the sealing layer (SL) isthe same as for the propylene copolymer composition (P) indicated above.

As mentioned above, the multi-layer polymer film shall be especiallysuitable for the packing industry. Accordingly good sealing propertiesare desired, like rather low heat sealing initiation temperature (SIT)and a broad sealing window combined with low stickiness.

Accordingly it is preferred that the sealing layer(s) (SL) and thus alsothe propylene copolymer composition (P) has/have a heat sealinginitiation temperature (SIT) of not more than 115° C., more preferablyof equal or below 110° C., still more preferably in the range of 90 to115° C., yet more preferably in the range of 93 to equal or below 110°C.

Alternatively or additionally the multi-layer polymer film has a heatsealing initiation temperature (SIT) of not more than 115° C., morepreferably of equal or below 110° C., still more preferably in the rangeof 90 to 115° C., yet more preferably in the range of 93 to equal orbelow 110° C.

Further it is appreciated that the sealing layer (SL) and/or thepropylene copolymer composition (P) has/have a broad heat sealing range.Accordingly it is preferred that the sealing layer (SL) and/or thepropylene copolymer composition (P) has/have a heat sealing range of atleast 20° C., more preferably of at least 25° C., yet more preferably ofat least 28° C., still more preferably in the range of 20 to 50° C.,still yet more preferably in the range of 25 to 45° C. The heat sealingrange is defined as the difference of heat sealing end temperature (SET)[° C.] and heat sealing initiation temperature (SIT) [° C.],[(SET)−(SIT)].

Alternatively or additionally the multi-layer polymer film has a heatsealing range of at least 20° C., more preferably of at least 25° C.,yet more preferably of at least 28° C., still more preferably in therange of 20 to 50° C., still yet more preferably in the range of 25 to45° C.

But not only the heat sealing initiation temperature (SIT) shall berather low but also the melting temperature (T_(m)) shall be ratherhigh. Accordingly the difference between the melting temperature (T_(m))and the heat sealing initiation temperature (SIT) shall be rather high.Thus it is preferred that the sealing layer(s) (SL) and/or the propylenecopolymer composition (P) fulfill(s) the equation (I), more preferablythe equation (Ia), still more preferably the equation (Ib),Tm−SIT≥22° C.  (I)Tm−SIT≥24° C.  (Ia)Tm−SIT≥27° C.  (Ib)wherein

-   Tm is the melting temperature given in centigrade [° C.] of the    sealing layer(s) (SL) and/or of the propylene copolymer composition    (P),-   SIT is the heat sealing initiation temperature (SIT) given in    centigrade [° C.] of the sealing layer(s) (SL) and/or of the    propylene copolymer composition (P).

The melting temperature (T_(m)) measured according to ISO 11357-3 of thesealing layer(s) (SL) and/or of the propylene copolymer composition (P)is preferably at least 125.0° C., more preferably of at least 128° C.,still more preferably of at least 135° C., like at least 140° C. Thus itis in particular appreciated that the melting temperature (T_(m))measured according to ISO 11357-3 of the sealing layer(s) (SL) and/or ofthe propylene copolymer composition (P) is in the range of 120 to 155°C., more preferably in the range of 122 to 150° C., still morepreferably in the range of 125 to 155° C., still yet more preferably inthe range of 120 to 150° C., like in the range of 125 to 150° C.

Additionally it is appreciated that the sealing layer(s) (SL) and/or thepropylene copolymer composition (P) of the instant invention has/have acrystallization temperature (T_(c)) measured according to ISO 11357-3 ofat least 88° C., more preferably of at least 90° C. Accordingly thesealing layer(s) (SL) and/or the propylene copolymer composition (P)has/have preferably a crystallization temperature (T_(c)) measuredaccording to ISO 11357-3 in the range of 88 to 115° C., more preferablyin the range of 90 to 110° C.

Additionally the sealing layer(s) (SL) and/or the propylene copolymercomposition (P) can be defined by the xylene cold soluble (XCS) content.Accordingly the sealing layer(s) (SL) and/or the propylene copolymercomposition (P) is/are preferably featured by a xylene cold soluble(XCS) content of below 25.0 wt.-%, more preferably of below 22.0 wt.-%,yet more preferably equal or below 20.0 wt.-%, still more preferablybelow 16.0 wt.-%. Thus it is in particular appreciated that the sealinglayer(s) (SL) and/or the propylene copolymer composition (P) of theinstant invention has/have a xylene cold soluble (XCS) content in therange of 0.5 to 25.0 wt.-%, more preferably in the range of 0.5 to 20.0wt.-%, yet more preferably in the range of 0.5 to 16.0 wt.-%.

The amount of xylene cold soluble (XCS) additionally indicates that thesealing layer(s) (SL) and/or the propylene copolymer composition (P)is/are preferably free of any elastomeric polymer component, like anethylene propylene rubber. In other words the sealing layer(s) (SL)and/or the propylene copolymer composition (P) shall be not aheterophasic polypropylene, i.e. a system consisting of a polypropylenematrix in which an elastomeric phase is dispersed. Such systems arefeatured by a rather high xylene cold soluble content. Accordingly in apreferred embodiment the propylene copolymer composition (P) comprisesthe polypropylene (A) and the propylene copolymer (B) as the onlypolymer components.

Similar to xylene cold solubles (XCS) the hexane hot soluble (HHS)indicate that part of a polymer which has a low crystallinity and whichis soluble in hexane at 50° C.

Accordingly it is preferred that the sealing layer(s) (SL) and/or thepropylene copolymer composition (P) has/have hexane hot solubles (HHS)measured according to FDA 177.1520 of not more than 2.5 wt.-%, morepreferably not more than 2.0 wt.-%, like not more than 1.5 wt.-%.

The propylene copolymer composition (P) of the present invention isfurther defined by its polymer fractions present. Accordingly thepropylene copolymer composition (P) of the present invention comprisesat least, preferably consists of, two fractions, namely thepolypropylene (A) and the propylene copolymer (B). Further thepolypropylene (A) is preferably the comonomer lean fraction whereas thepropylene copolymer (B) is the comonomer rich fraction.

Thus it is appreciated that the polypropylene (A) has a comonomercontent of equal or below 5.0 wt.-%, more preferably of equal or below4.0 wt.-%. Accordingly the polypropylene (A) can be a propylenehomopolymer (H-A) or a propylene copolymer (C-A).

The expression homopolymer used in the instant invention relates to apolypropylene that consists of at least 99.5 wt.-%, more preferably ofat least 99.8 wt.-%, of propylene units. In a preferred embodiment onlypropylene units in the propylene homopolymer are detectable.

In case the polypropylene (A) is a propylene copolymer (C-A) thecomonomer content is in the range of 0.2 to equal or below 5.0 wt.-%,preferably in the range 0.5 to equal or below 4.0 wt.-%. More preferablythe propylene copolymer (C-A) is a random propylene copolymer. Thecomonomers of the propylene copolymer (C-A) are C₅ to C₁₂ α-olefins,more preferably the comonomers of the propylene copolymer (C-A) areselected from the group of C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂ α-olefin,still more preferably the comonomers of the propylene copolymer (C-A)are 1-hexene and/or 1-octene. The propylene copolymer (C-A) may containmore than one type of comonomer. Thus the propylene copolymer (C-A) ofthe present invention may contain one, two or three differentcomonomers. However it is preferred that the propylene copolymer (C-A)contains only one type of comonomer. Preferably the propylene copolymer(C-A) comprises—apart from propylene—only 1-hexene and/or 1-octene. Inan especially preferred embodiment the comonomer of the propylenecopolymer (C-A) is only 1-hexene.

Thus the propylene copolymer (C-A) is in one preferred embodiment apropylene copolymer of propylene and 1-hexene only, wherein the 1-hexenecontent is in the range of 0.2 to 5.0 wt-%, preferably in the range of0.5 to equal or below 4.0 wt-%.

The propylene copolymer (B) has preferably a higher comonomer contentthan the polypropylene (A). Accordingly the propylene copolymer (B) hasa comonomer content of equal or more than 2.5 wt.-% to 20.0 wt.-%, morepreferably of equal or more than 3.0 to 15.0 wt.-%, still morepreferably of equal or more than 4.0 to 10.0 wt.-%.

More preferably the propylene copolymer (B) is a random propylenecopolymer.

The comonomers of the propylene copolymer (B) are C₅ to C₁₂ α-olefins,more preferably the comonomers of the propylene copolymer (B) areselected from the group of C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂ α-olefin,still more preferably the comonomers of the propylene copolymer (B) are1-hexene and/or 1-octene. The propylene copolymer (B) may contain morethan one type of comonomer. Thus the propylene copolymer (B) of thepresent invention may contain one, two or three different comonomers.However it is preferred that the propylene copolymer (B) contains onlyone type of comonomer. Preferably the propylene copolymer (B)comprises—apart from propylene—only 1-hexene and/or 1-octene. In anespecially preferred embodiment the comonomer of the propylene copolymer(B) is only 1-hexene.

Thus the propylene copolymer (C-A) is in one preferred embodiment apropylene copolymer of propylene and 1-hexene only, wherein the 1-hexenecontent is in the range of 0.2 to 5.0 wt-%, preferably in the range of0.5 to equal or below 4.0 wt-%.

The propylene copolymer (B) has preferably a higher comonomer contentthan the polypropylene (A). Accordingly the propylene copolymer (B) hasa comonomer content of equal or more than 2.5 wt.-% to 20.0 wt.-%, morepreferably of equal or more than 3.0 to 15.0 wt.-%, still morepreferably of equal or more than 4.0 to 12.0 wt.-%.

More preferably the propylene copolymer (B) is a random propylenecopolymer.

The comonomers of the propylene copolymer (B) are C₅ to C₁₂ α-olefins,more preferably the comonomers of the propylene copolymer (B) areselected from the group of C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂ α-olefin,still more preferably the comonomers of the propylene copolymer (B) are1-hexene and/or 1-octene. The propylene copolymer (B) may contain morethan one type of comonomer. Thus the propylene copolymer (B) of thepresent invention may contain one, two or three different comonomers.However it is preferred that the propylene copolymer (B) contains onlyone type of comonomer. Preferably the propylene copolymer (B)comprises—apart from propylene—only 1-hexene and/or 1-octene. In anespecially preferred embodiment the comonomer of the propylene copolymer(B) is only 1-hexene.

Thus the propylene copolymer (B) is in a preferred embodiment apropylene copolymer of propylene and 1-hexene only, wherein the 1-hexenecontent is in the range of equal or more than 2.5 wt.-% to 20.0 wt.-%,more preferably of equal or more than 3.0 to 15.0 wt.-%, still morepreferably of equal or more than 4.0 to 12.0 wt.-%.

It is in particular preferred that the comonomers of the propylenecopolymer (C-A) and of the propylene copolymer (B) are the same.Accordingly in one preferred embodiment the propylene copolymercomposition (P) of the instant invention comprises, preferably comprisesonly, a propylene copolymer (C-A) and a propylene copolymer (B), in bothpolymers the comonomer is only 1-hexene.

In another preferred embodiment the propylene copolymer composition (P)of the instant invention comprises, preferably comprises only, apropylene homopolymer (H-A) and a propylene copolymer (B), wherein thecomonomers of the propylene copolymer (B) are selected from the groupconsisting of C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈ α-olefin, C₉α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂ α-olefin, preferably thecomonomers of the propylene copolymer (B) are 1-hexene and/or 1-octene,more preferably the comonomer of the propylene copolymer (B) is 1-hexeneonly.

As mentioned above polypropylene (A) is preferably the comonomer leanfraction whereas the propylene copolymer (B) is the comonomer richfraction. Accordingly the comonomer content in the polypropylene (A) islower compared to the comonomer content of the propylene copolymer (B).Thus it is appreciated that the propylene copolymer composition (P) andthe polypropylene (A) fulfil together the correlation [com (P)−com (A)]being at least 1.0, i.e. in the range of 1.0 to 6.0, more preferablybeing in the range of 1.0 to 4.5, still more preferably in the range of1.5 to 4.0,

wherein

-   com (A) is the comonomer content of the polypropylene (A) given in    weight percent [wt.-%],-   com (P) is the comonomer content of the propylene copolymer    composition (P) given in weight percent [wt.-%].

The equation is in particular applicable in case the polypropylene (A)is a propylene copolymer (C-A) as defined above.

One important aspect of the present invention is that the polypropylene(A) and the propylene copolymer (B) of the propylene copolymercomposition (P) differ in the comonomer content. Additionally thepolypropylene (A) and the propylene copolymer (B) of the propylenecopolymer composition (P) may also differ in the melt flow rate.Accordingly the ratio MFR (A)/MFR (P) is equal or below 1.0, morepreferably equal or below 0.70, yet more preferably equal or below 0.60,still more preferably equal or below 0.55,

wherein

-   MFR (A) is the melt flow rate MFR₂ (230° C.) [g/10 min] measured    according to ISO 1133 of the polypropylene (A),-   MFR (P) is the melt flow rate MFR₂ (230° C.) [g/10 min] measured    according to ISO 1133 of the propylene copolymer composition (P).

Further it is appreciated that the polypropylene (A) has a melt flowrate MFR₂ (230° C.) measured according to ISO 1133 of at least 0.5 g/10min, more preferably of at least 1.5 g/10 min, still more preferably inthe range of 1.0 to 8.0 g/10 min, still more preferably in the range of1.5 to 7.0 g/10 min, yet more preferably in the range of 2.0 to 5.0 g/10min, like in the range of 2.5 to 5.0 g/10 min.

As a high melt flow rate indicates a low molecular weight, it isappreciated that the polypropylene (A) has a weight average molecularweight (M_(w)) of below 450 kg/mol, still more preferably of below 400kg/mol, yet more preferably in the range of 150 to below 450 kg/mol,like in the range of 180 to 400 kg/mol.

Further the polypropylene (A) has preferably a xylene cold soluble (XCS)content of below 2.5 wt.-%, more preferably of below 2.0 wt.-%, stillmore preferably in the range of 0.3 to 2.5 wt.-%, yet more preferably inthe range of 0.3 to 2.0 wt.-%. It is in particular preferred that thepropylene copolymer (A) has a lower xylene cold soluble (XCS) contentthan the propylene copolymer (B).

The propylene copolymer composition (P) may contain additives known inthe art, like antioxidants, nucleating agents, slip agents andantistatic agents. The polymer fraction, preferably the sum of thepolypropylene (A) and the propylene copolymer (B) fractions, is at least90 wt.-%, more preferably at least 95 wt.-%, still more preferably atleast 98 wt.-%, like at least 99 wt.-%.

In the following the preparation of the multi-layer film is defined inmore detail.

The polymers used for the core layer (CL) are known in the art and arenot on focus in this invention. Typical commercially available polyvinylalcohols, polyacrylates, polyamides, polyolefins (PO), like propylenehomopolymer (H-PP), can be used for the core layer (CL).

The propylene copolymer composition (P) is preferably obtained by asequential polymerization process comprising at least two reactorsconnected in series, wherein said process comprises the steps of

-   (A) polymerizing in a first reactor (R-1) being a slurry reactor    (SR), preferably a loop reactor (LR), propylene and optionally at    least one C₅ to C₁₂ α-olefin, preferably 1-hexene, obtaining a    polypropylene (A) as defined in the instant invention,-   (B) transferring said polypropylene (A) and unreacted comonomers of    the first reactor in a second reactor (R-2) being a gas phase    reactor (GPR-1),-   (C) feeding to said second reactor (R-2) propylene and at least one    C₅ to C₁₂ α-olefin,-   (D) polymerizing in said second reactor (R-2) and in the presence of    said first polypropylene (A) propylene and at least one C₅ to C₁₂    α-olefin obtaining a propylene copolymer (B) as defined in the    instant invention, said polypropylene (A) and said propylene    copolymer (B) form the propylene copolymer composition (P) as    defined in the instant invention,    wherein further    in the first reactor (R-1) and second reactor (R-2) the    polymerization takes place in the presence of a solid catalyst    system (SCS), said solid catalyst system (SCS) comprises-   (i) a transition metal compound of formula (I)    R_(n)(Cp′)₂MX₂  (I)    -   wherein    -   “M” is zirconium (Zr) or hafnium (Hf),    -   each “X” is independently a monovalent anionic σ-ligand,    -   each “Cp′” is a cyclopentadienyl-type organic ligand        independently selected from the group consisting of substituted        cyclopentadienyl, substituted indenyl, substituted        tetrahydroindenyl, and substituted or unsubstituted fluorenyl,        said organic ligands coordinate to the transition metal (M),    -   “R” is a bivalent bridging group linking said organic ligands        (Cp′),    -   “n” is 1 or 2, preferably 1, and-   (ii) optionally a cocatalyst (Co) comprising an element (E) of group    13 of the periodic table (IUPAC), preferably a cocatalyst (Co)    comprising a compound of Al.

Concerning the definition of the propylene copolymer composition (P),the polypropylene (A) and the propylene copolymer (B) it is referred tothe definitions given above.

The term “sequential polymerization process” indicates that thepropylene copolymer composition (P) is produced in at least two reactorsconnected in series. Accordingly, a decisive aspect of the presentprocess is the preparation of the propylene copolymer composition (P) intwo different reactors. Thus the present process comprises at least afirst reactor (R-1) and a second reactor (R-2). In one specificembodiment the instant process consists of two polymerization reactors(R-1) and (R-2). The term “polymerization reactor” shall indicate thatthe main polymerization takes place. Thus in case the process consistsof two polymerization reactors, this definition does not exclude theoption that the overall process comprises for instance apre-polymerization step in a pre-polymerization reactor. The term“consists of” is only a closing formulation in view of the mainpolymerization reactors.

The first reactor (R-1) is preferably a slurry reactor (SR) and can beany continuous or simple stirred batch tank reactor or loop reactoroperating in bulk or slurry. Bulk means a polymerization in a reactionmedium that comprises of at least 60% (wt/wt), preferably 100% monomer.According to the present invention the slurry reactor (SR) is preferablya (bulk) loop reactor (LR).

The second reactor (R-2) and any subsequent reactor are preferably gasphase reactors (GPR). Such gas phase reactors (GPR) can be anymechanically mixed or fluid bed reactors. Preferably the gas phasereactors (GPR) comprise a mechanically agitated fluid bed reactor withgas velocities of at least 0.2 m/sec. Thus it is appreciated that thegas phase reactor is a fluidized bed type reactor preferably with amechanical stirrer.

The condition (temperature, pressure, reaction time, monomer feed) ineach reactor is dependent on the desired product which is in theknowledge of a person skilled in the art. As already indicated above,the first reactor (R-1) is preferably a slurry reactor (SR), like a loopreactor (LR), whereas the second reactor (R-2) is preferably a gas phasereactor (GPR-1). The subsequent reactors—if present—are also preferablygas phase reactors (GPR).

A preferred multistage process is a “loop-gas phase”-process, such asdeveloped by Borealis A/S, Denmark (known as BORSTAR® technology)described e.g. in patent literature, such as in EP 0 887 379 or in WO92/12182.

Multimodal polymers can be produced according to several processes whichare described, e.g. in WO 92/12182, EP 0 887 379, and WO 98/58976. Thecontents of these documents are included herein by reference.

Preferably, in the instant process for producing propylene copolymercomposition (P) as defined above the conditions for the first reactor(R-1), i.e. the slurry reactor (SR), like a loop reactor (LR), of step(A) may be as follows:

-   -   the temperature is within the range of 40° C. to 110° C.,        preferably between 60° C. and 100° C., 70 to 90° C.,    -   the pressure is within the range of 20 bar to 80 bar, preferably        between 40 bar to 70 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

Subsequently, the reaction mixture from step (A) is transferred to thesecond reactor (R-2), i.e. gas phase reactor (GPR-1), i.e. to step (D),whereby the conditions in step (D) are preferably as follows:

-   -   the temperature is within the range of 50° C. to 130° C.,        preferably between 60° C. and 100° C.,    -   the pressure is within the range of 5 bar to 50 bar, preferably        between 15 bar to 40 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

The residence time can vary in both reactor zones.

In one embodiment of the process for producing propylene copolymercomposition (P) the residence time in bulk reactor, e.g. loop is in therange 0.2 to 4 hours, e.g. 0.3 to 1.5 hours and the residence time ingas phase reactor will generally be 0.2 to 6.0 hours, like 0.5 to 4.0hours.

If desired, the polymerization may be effected in a known manner undersupercritical conditions in the first reactor (R-1), i.e. in the slurryreactor (SR), like in the loop reactor (LR), and/or as a condensed modein the gas phase reactor (GPR-1).

The conditions in the other gas phase reactors (GPR), if present, aresimilar to the second reactor (R-2).

The present process may also encompass a pre-polymerization prior to thepolymerization in the first reactor (R-1). The pre-polymerization can beconducted in the first reactor (R-1), however it is preferred that thepre-polymerization takes place in a separate reactor, so calledpre-polymerization reactor.

In one specific embodiment the solid catalyst system (SCS) has aporosity measured according ASTM 4641 of less than 1.40 ml/g and/or asurface area measured according to ASTM D 3663 of lower than 25 m²/g.

Preferably the solid catalyst system (SCS) has a surface area of lowerthan 15 m²/g, yet still lower than 10 m²/g and most preferred lower than5 m²/g, which is the lowest measurement limit. The surface areaaccording to this invention is measured according to ASTM D 3663 (N₂).

Alternatively or additionally it is appreciated that the solid catalystsystem (SCS) has a porosity of less than 1.30 ml/g and more preferablyless than 1.00 ml/g. The porosity has been measured according to ASTM4641 (N₂). In another preferred embodiment the porosity is notdetectable when determined with the method applied according to ASTM4641 (N₂).

Furthermore the solid catalyst system (SCS) typically has a meanparticle size of not more than 500 μm, i.e. preferably in the range of 2to 500 μm, more preferably 5 to 200 μm. It is in particular preferredthat the mean particle size is below 80 μm, still more preferably below70 μm. A preferred range for the mean particle size is 5 to 70 μm, oreven 10 to 60 μm.

As stated above the transition metal (M) is zirconium (Zr) or hafnium(Hf), preferably zirconium (Zr).

The term “σ-ligand” is understood in the whole description in a knownmanner, i.e. a group bound to the metal via a sigma bond. Thus theanionic ligands “X” can independently be halogen or be selected from thegroup consisting of R′, OR′, SiR′₃, OSiR′₃, OSO₂CF₃, OCOR′, SR′, NR′₂ orPR′₂ group wherein R′ is independently hydrogen, a linear or branched,cyclic or acyclic, C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl, C₂ to C₂₀alkynyl, C₃ to C₁₂ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ arylalkyl, C₇to C₂₀ alkylaryl, C₈ to C₂₀ arylalkenyl, in which the R′ group canoptionally contain one or more heteroatoms belonging to groups 14 to 16.In a preferred embodiments the anionic ligands “X” are identical andeither halogen, like Cl, or methyl or benzyl.

A preferred monovalent anionic ligand is halogen, in particular chlorine(Cl).

The substituted cyclopentadienyl-type ligand(s) may have one or moresubstituent(s) being selected from the group consisting of halogen,hydrocarbyl (e.g. C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl, C₂ to C₂₀ alkynyl,C₃ to C₂₀ cycloalkyl, like C₁ to C₂₀ alkyl substituted C₅ to C₂₀cycloalkyl, C₆ to C₂₀ aryl, C₅ to C₂₀ cycloalkyl substituted C₁ to C₂₀alkyl wherein the cycloalkyl residue is substituted by C₁ to C₂₀ alkyl,C₇ to C₂₀ arylalkyl, C₃ to C₁₂ cycloalkyl which contains 1, 2, 3 or 4heteroatom(s) in the ring moiety, C₆ to C₂₀-heteroaryl, C₁ toC₂₀-haloalkyl, —SiR″₃, —SR″, —PR″₂ or —NR″₂, each R″ is independently ahydrogen or hydrocarbyl (e. g. C₁ to C₂₀ alkyl, C₁ to C₂₀ alkenyl, C₂ toC₂₀ alkynyl, C₃ to C₁₂ cycloalkyl, or C₆ to C₂₀ aryl) or e.g. in case of—NR″₂, the two substituents R″ can form a ring, e.g. five- orsix-membered ring, together with the nitrogen atom wherein they areattached to.

Further “R” of formula (I) is preferably a bridge of 1 to 4 atoms, suchatoms being independently carbon (C), silicon (Si), germanium (Ge) oroxygen (O) atom(s), whereby each of the bridge atoms may bearindependently substituents, such as C₁ to C₂₀-hydrocarbyl, tri(C₁ toC₂₀-alkyl)silyl, tri(C₁ to C₂₀-alkyl)siloxy and more preferably “R” is aone atom bridge like e.g. —SiR′″₂—, wherein each R′″ is independently C₁to C₂₀-alkyl, C₂ to C₂₀-alkenyl, C₂ to C₂₀-alkynyl, C₃ to C₁₂cycloalkyl, C₆ to C₂₀-aryl, alkylaryl or arylalkyl, or tri(C₁ to C₂₀alkyl)silyl-residue, such as trimethylsilyl-, or the two R′″ can be partof a ring system including the Si bridging atom.

In a preferred embodiment the transition metal compound has the formula(II)

wherein

-   M is zirconium (Zr) or hafnium (Hf), preferably zirconium (Zr),-   X are ligands with a σ-bond to the metal “M”, preferably those as    defined above for formula (I),-    preferably chlorine (Cl) or methyl (CH₃), the former especially    preferred,-   R¹ are equal to or different from each other, preferably equal to,    and are selected from the group consisting of linear saturated C₁ to    C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched saturated    C₁-C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀    cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, and C₇ to C₂₀    arylalkyl, optionally containing one or more heteroatoms of groups    14 to 16 of the Periodic Table (IUPAC),-    preferably are equal to or different from each other, preferably    equal to, and are C₁ to C₁₀ linear or branched hydrocarbyl, more    preferably are equal to or different from each other, preferably    equal to, and are C₁ to C₆ linear or branched alkyl,-   R² to R⁶ are equal to or different from each other and are selected    from the group consisting of hydrogen, linear saturated C₁-C₂₀    alkyl, linear unsaturated C₁-C₂₀ alkyl, branched saturated C₁-C₂₀    alkyl, branched unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀    aryl, C₇-C₂₀ alkylaryl, and C₇-C₂₀ arylalkyl, optionally containing    one or more heteroatoms of groups 14 to 16 of the Periodic Table    (IUPAC), preferably are equal to or different from each other and    are C₁ to C₁₀ linear or branched hydrocarbyl, more preferably are    equal to or different from each other and are C₁ to C₆ linear or    branched alkyl,-   R⁷ and R⁸ are equal to or different from each other and selected    from the group consisting of hydrogen, linear saturated C₁ to C₂₀    alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to    C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀    cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, C₇ to C₂₀    arylalkyl, optionally containing one or more heteroatoms of groups    14 to 16 of the Periodic Table (IUPAC), SiR¹⁰ ₃, GeR¹⁰ ₃, OR¹⁰, SR¹⁰    and NR¹⁰ ₂,-    wherein    -   R¹⁰ is selected from the group consisting of linear saturated        C₁-C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched        saturated C₁ to C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl,        C₃ to C₂₀ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, and        C₇ to C₂₀ arylalkyl, optionally containing one or more        heteroatoms of groups 14 to 16 of the Periodic Table (IUPAC),-    and/or    -   R⁷ and R⁸ being optionally part of a C₄ to C₂₀ carbon ring        system together with the indenyl carbons to which they are        attached, preferably a C₅ ring, optionally one carbon atom can        be substituted by a nitrogen, sulfur or oxygen atom,-   R⁹ are equal to or different from each other and are selected from    the group consisting of hydrogen, linear saturated C₁ to C₂₀ alkyl,    linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to C₂₀    alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl,    C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, C₇ to C₂₀ arylalkyl, OR¹⁰, and    SR¹⁰, preferably R⁹ are equal to or different from each other and    are H or CH₃,-    wherein    -   R¹⁰ is defined as before,-   L is a bivalent group bridging the two indenyl ligands, preferably    being a C₂R¹¹ ₄ unit or a SiR¹¹ ₂ or GeR¹¹ ₂, wherein,    -   R¹¹ is selected from the group consisting of H, linear saturated        C₁ to C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched        saturated C₁ to C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl,        C₃ to C₂₀ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl or C₇        to C₂₀ arylalkyl, optionally containing one or more heteroatoms        of groups 14 to 16 of the Periodic Table (IUPAC),    -   preferably Si(CH₃)₂, SiCH₃C₆H₁₁, or SiPh₂,    -   wherein C₆H₁₁ is cyclohexyl.

Preferably the transition metal compound of formula (II) is C₂-symmetricor pseudo-C₂-symmetric. Concerning the definition of symmetry it isreferred to Resconi et al. Chemical Reviews, 2000, Vol. 100, No. 4 1263and references herein cited.

Preferably the residues R¹ are equal to or different from each other,more preferably equal, and are selected from the group consisting oflinear saturated C₁ to C₁₀ alkyl, linear unsaturated C₁ to C₁₀ alkyl,branched saturated C₁ to C₁₀ alkyl, branched unsaturated C₁ to C₁₀ alkyland C₇ to C₁₂ arylalkyl. Even more preferably the residues R¹ are equalto or different from each other, more preferably equal, and are selectedfrom the group consisting of linear saturated C₁ to C₆ alkyl, linearunsaturated C₁ to C₆ alkyl, branched saturated C₁ to C₆ alkyl, branchedunsaturated C₁ to C₆ alkyl and C₇ to C₁₀ arylalkyl. Yet more preferablythe residues R¹ are equal to or different from each other, morepreferably equal, and are selected from the group consisting of linearor branched C₁ to C₄ hydrocarbyl, such as for example methyl or ethyl.

Preferably the residues R² to R⁶ are equal to or different from eachother and linear saturated C₁ to C₄ alkyl or branched saturated C₁ to C₄alkyl. Even more preferably the residues R² to R⁶ are equal to ordifferent from each other, more preferably equal, and are selected fromthe group consisting of methyl, ethyl, iso-propyl and tert-butyl.

Preferably R⁷ and R⁸ are equal to or different from each other and areselected from hydrogen and methyl, or they are part of a 5-methylenering including the two indenyl ring carbons to which they are attached.In another preferred embodiment, R⁷ is selected from OCH₃ and OC₂H₅, andR⁸ is tert-butyl.

In a preferred embodiment the transition metal compound israc-methyl(cyclohexyl)silanediylbis(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride.

In a second preferred embodiment, the transition metal compound israc-dimethylsilanediylbis(2-methyl-4-phenyl-1,5,6,7-tetrahydro-s-indacen-1-yl)zirconiumdichloride.

In a third preferred embodiment, the transition metal compound israc-dimethylsilanediylbis(2-methyl-4-phenyl-5-methoxy-6-tert-butylindenyl)zirconiumdichloride.

As a further requirement the solid catalyst system (SCS) according tothis invention must comprise a cocatalyst (Co) comprising an element (E)of group 13 of the periodic table (IUPAC), for instance the cocatalyst(Co) comprises a compound of Al.

Examples of such cocatalyst (Co) are organo aluminium compounds, such asaluminoxane compounds.

Such compounds of Al, preferably aluminoxanes, can be used as the onlycompound in the cocatalyst (Co) or together with other cocatalystcompound(s). Thus besides or in addition to the compounds of Al, i.e.the aluminoxanes, other cation complex forming cocatalyst compounds,like boron compounds can be used. Said cocatalysts are commerciallyavailable or can be prepared according to the prior art literature.Preferably however in the manufacture of the solid catalyst system onlycompounds of Al as cocatalyst (Co) are employed.

In particular preferred cocatalysts (Co) are the aluminoxanes, inparticular the C1 to C10-alkylaluminoxanes, most particularlymethylaluminoxane (MAO).

Preferably, the organo-zirconium compound of formula (I) and thecocatalyst (Co) of the solid catalyst system (SCS) represent at least 70wt %, more preferably at least 80 wt %, even more preferably at least 90wt %, even further preferably at least 95 wt % of the solid catalystsystem. Thus it is appreciated that the solid catalyst system isfeatured by the fact that it is self-supported, i.e. it does notcomprise any catalytically inert support material, like for instancesilica, alumina or MgCl₂ or porous polymeric material, which isotherwise commonly used in heterogeneous catalyst systems, i.e. thecatalyst is not supported on external support or carrier material. As aconsequence of that the solid catalyst system (SCS) is self-supportedand it has a rather low surface area.

In one embodiment the solid metallocene catalyst system (SCS) isobtained by the emulsion solidification technology, the basic principlesof which are described in WO 03/051934. This document is herewithincluded in its entirety by reference.

Hence the solid catalyst system (SCS) is preferably in the form of solidcatalyst particles, obtainable by a process comprising the steps of

-   a) preparing a solution of one or more catalyst components;-   b) dispersing said solution in a second solvent to form an emulsion    in which said one or more catalyst components are present in the    droplets of the dispersed phase,-   c) solidifying said dispersed phase to convert said droplets to    solid particles and optionally recovering said particles to obtain    said catalyst.

Preferably a first solvent, more preferably a first organic solvent, isused to form said solution. Still more preferably the organic solvent isselected from the group consisting of a linear alkane, cyclic alkane,aromatic hydrocarbon and halogen-containing hydrocarbon.

Moreover the second solvent forming the continuous phase is an inertsolvent towards to catalyst components, The second solvent might beimmiscible towards the solution of the catalyst components at leastunder the conditions (like temperature) during the dispersing step. Theterm “immiscible with the catalyst solution” means that the secondsolvent (continuous phase) is fully immiscible or partly immiscible i.e.not fully miscible with the dispersed phase solution.

Preferably the immiscible solvent comprises a fluorinated organicsolvent and/or a functionalized derivative thereof, still morepreferably the immiscible solvent comprises a semi-, highly- orperfluorinated hydrocarbon and/or a functionalized derivative thereof.It is in particular preferred, that said immiscible solvent comprises aperfluorohydrocarbon or a functionalized derivative thereof, preferablyC₃-C₃₀ perfluoroalkanes, -alkenes or -cycloalkanes, more preferredC₄-C₁₀ perfluoro-alkanes, -alkenes or -cycloalkanes, particularlypreferred perfluorohexane, perfluoroheptane, perfluorooctane orperfluoro (methylcyclohexane) or perfluoro (1,3-dimethylcyclohexane) ora mixture thereof.

Furthermore it is preferred that the emulsion comprising said continuousphase and said dispersed phase is a bi- or multiphasic system as knownin the art. An emulsifier may be used for forming and stabilising theemulsion. After the formation of the emulsion system, said catalyst isformed in situ from catalyst components in said solution.

In principle, the emulsifying agent may be any suitable agent whichcontributes to the formation and/or stabilization of the emulsion andwhich does not have any adverse effect on the catalytic activity of thecatalyst. The emulsifying agent may e.g. be a surfactant based onhydrocarbons optionally interrupted with (a) heteroatom(s), preferablyhalogenated hydrocarbons optionally having a functional group,preferably semi-, highly- or perfluorinated hydrocarbons as known in theart. Alternatively, the emulsifying agent may be prepared during theemulsion preparation, e.g. by reacting a surfactant precursor with acompound of the catalyst solution. Said surfactant precursor may be ahalogenated hydrocarbon with at least one functional group, e.g. ahighly fluorinated C1-n (suitably C4-30- or C5-15) alcohol (e.g. highlyfluorinated heptanol, octanol or nonanol), oxide (e.g. propenoxide) oracrylate ester which reacts e.g. with a cocatalyst component, such asaluminoxane to form the “actual” surfactant.

In principle any solidification method can be used for forming the solidparticles from the dispersed droplets. According to one preferableembodiment the solidification is effected by a temperature changetreatment. Hence the emulsion subjected to gradual temperature change ofup to 10° C./min, preferably 0.5 to 6° C./min and more preferably 1 to5° C./min. Even more preferred the emulsion is subjected to atemperature change of more than 40° C., preferably more than 50° C.within less than 10 seconds, preferably less than 6 seconds.

For further details, embodiments and examples of the continuous anddispersed phase system, emulsion formation method, emulsifying agent andsolidification methods reference is made e.g. to the above citedinternational patent application WO 03/051934.

All or part of the preparation steps can be done in a continuous mannerReference is made to WO 2006/069733 describing principles of suchcontinuous or semicontinuous preparation methods of the solid catalysttypes, prepared via emulsion/solidification method.

The above described catalyst components are prepared according to themethods described in WO 01/48034.

The multi-layer polymer film of the instant invention is obtained bycoextruding the core layer (CL) on the one side with a propylenecopolymer composition (P) obtaining the sealing layer (SL). Optionallyon the other side of the core layer (CL) an outer layer (OL), forinstance an outer layer (OL), a second sealing layer (SL) or a metallayer (ML) can be placed. The second sealing layer (SL) is preferablymade also from a propylene copolymer composition (P) according to thisinvention whereas the outer layer (OL) is preferably a polypropylene(PP) or a polyethylene (PE).

The layered structure of the multi-layer polymer film of the inventionmay be prepared by any conventional film formation process includingextrusion procedures, such as cast film extrusion. Preferred method iscoextrusion on a cast film line.

It is in particular preferred that the multi-layer polymer film is notsubjected a stretching step.

In case the multi-layer polymer film is produced by cast film technologythe molten polymers are extruded through slot extrusion dies onto achill roll to cool the polymers to a solid film of at least two layers.For the production of the multi-layer polymer film the process iscarried out by coextruding the melts of the polymer composition, i.e.the polymer for the core layer (CL), the propylene copolymer composition(P) for the sealing layer (SL) and optionally the polymer for the outerlayer (OL) or for a further sealing layer (SL), corresponding to theindividual layers of the multi-layer polymer film through flat-filmmultilayer die, taking off the resultant multi-layer polymer film overone or more rolls for solidification. As it is conventional in thecoextrusion process, the polymer of each respective individual layer isfirstly compressed and liquefied in an extruder, it being possible forany additives to be already added to the polymer or introduced at thisstage via a masterbatch. The melts are then forced simultaneouslythrough a flat-film die (slot die), and the extruded multi-layer polymerfilm is taken off on one or more take-off rolls, during which it coolsand solidifies. It has proven particularly favorable to keep thetake-off roll or rolls, by means of which the extruded film is cooledand solidified, at a temperature from 10 to 50 C, preferably from 15 to40 C. Subsequently the metal layer (ML) is applied, if present.

Optionally one or both, surface (s) of the multi-layer polymer film canbe corona- or flame-treated by one of the known methods. For the coronatreatment, the film is passed between two conductor elements serving aselectrodes, with such a high voltage, usually an alternating voltage(about 10000 V and 10000 Hz), being applied between the electrodes thatspray or corona discharges can occur. Due to the spray or coronadischarge, the air above the film surface is ionized and reacts with themolecules of the film surface, causing formation of polar inclusions inthe essentially non-polar polymer matrix. The treatment intensities arein the usual range, preferably from 38 to 45 dynes/cm after production.

Furthermore the present invention is also directed to the use of theinventive multi-layer polymer film as packing material, in particular asa as packing material, in particular as a packing material for foodand/or non-food products like textiles, flowers, carton boxes containingtobacco product or perfumes.

In the following, the present invention is described by way of examples.

EXAMPLES A. Measuring Methods

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

Quantification of Microstructure by NMR Spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used toquantify the isotacticity, regio-regularity and comonomer content of thepolymers. Quantitative ¹³C{¹H} NMR spectra recorded in the molten-stateusing a Bruker Advance III 500 NMR spectrometer operating at 500.13 and125.76 MHz for ¹H and ¹³C respectively. All spectra were recorded usinga ¹³C optimised 7 mm magic-angle spinning (MAS) probehead at 180° C.using nitrogen gas for all pneumatics. Approximately 200 mg of materialwas packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4kHz. Standard single-pulse excitation was employed utilising the NOE atshort recycle delays (as described in Pollard, M., Klimke, K., Graf, R.,Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W.,Macromolecules 2004, 37, 813, and in Klimke, K., Parkinson, M., Piel,C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys.2006, 207, 382) and the RS-HEPT decoupling scheme (as described inFilip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239, and inGriffin, J. M., Tripon, C., Samoson, A., Filip, C., and Brown, S. P.,Mag. Res. in Chem. 2007, 45, S1, S198). A total of 1024 (1 k) transientswere acquired per spectra.

Quantitative ¹³C{¹H} NMR spectra were processed, integrated and relevantquantitative properties determined from the integrals. All chemicalshifts are internally referenced to the methyl isotactic pentad (mmmm)at 21.85 ppm. The tacticity distribution was quantified throughintegration of the methyl region in the ¹³C{¹H} spectra, correcting forany signal not related to the primary (1, 2) inserted propene stereosequences, as described in Busico, V., Cipullo, R., Prog. Polym. Sci.2001, 26, 443 and in Busico, V., Cipullo, R., Monaco, G., Vacatello, M.,Segre, A. L., Macromolecules 1997, 30, 6251.

Characteristic signals corresponding to regio defects were observed(Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000,100, 1253). The influence of regio defects on the quantification of thetacticity distribution was corrected for by subtraction ofrepresentative regio defect integrals from specific integrals of thestereo sequences.

The isotacticity was determined at the triad level and reported as thepercentage of isotactic triad mm with respect to all triad sequences:% mm=(mm/(mm+mr+rr))*100

Characteristic signals corresponding to the incorporation of 1-hexenewere observed, and the 1-hexene content was calculated as the molepercent of 1-hexene in the polymer, H (mol %), according to:[H]=H _(tot)/(P _(tot) +H _(tot))where:H _(tot) =I(αB ₄)/2+I(ααB ₄)×2where I(α B₄) is the integral of the α B₄ sites at 44.1 ppm, whichidentifies the isolated 1-hexene incorporated in PPHPP sequences, andI(ααB₄) is the integral of the ααB₄ sites at 41.6 ppm, which identifiesthe consecutively incorporated 1-hexene in PPHHPP sequences.

P_(tot)=Integral of all CH3 areas on the methyl region with correctionapplied for underestimation of other propene units not accounted for inthis region and overestimation due to other sites found in this region.and H(mol %)=100×[H]which is then converted into wt % using the correlationH(wt %)=(100×H mol %×84.16)/(H mol %×84.16+(100−H mol %)×42.08)

A statistical distribution is suggested from the relationship betweenthe content of hexene present in isolated (PPHPP) and consecutive(PPHHPP) incorporated comonomer sequences:[HH]<[H]²

Calculation of Comonomer Content of the Propylene Copolymer (B)

$\frac{{C(P)} - {{w(A)} \times {C(A)}}}{w(B)} = {C(B)}$wherein

-   w(A) is the weight fraction of the polypropylene (A),-   w(B) is the weight fraction of the propylene copolymer (B),-   C(A) is the comonomer content [in wt.-%] measured by ¹³C NMR    spectroscopy of the polypropylene (A), i.e. of the product of the    first reactor (R1),-   C(P) is the comonomer content [in wt.-%] measured by ¹³C NMR    spectroscopy of the propylene copolymer composition (P)],-   C(B) is the calculated comonomer content [in wt.-%] of the the    propylene copolymer (B)

Mw, Mn, MWD

Mw/Mn/MWD are measured by Gel Permeation Chromatography (GPC) accordingto the following method:

The weight average molecular weight (Mw), the number average molecularweight (Mn), and the molecular weight distribution (MWD=Mw/Mn) ismeasured by a method based on ISO 16014-1:2003 and ISO 16014-4:2003. AWaters Alliance GPCV 2000 instrument, equipped with refractive indexdetector and online viscosimeter is used with 3×TSK-gel columns(GMHXL-HT) from TosoHaas and 1,2,4-trichlorobenzene (TCB, stabilizedwith 200 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 145° C.and at a constant flow rate of 1 mL/min. 216.5 μL of sample solution areinjected per analysis. The column set is calibrated using relativecalibration with 19 narrow MWD polystyrene (PS) standards in the rangeof 0.5 kg/mol to 11 500 kg/mol and a set of well characterized broadpolypropylene standards. All samples are prepared by dissolving 5 to 10mg of polymer in 10 mL (at 160° C.) of stabilized TCB (same as mobilephase) and keeping for 3 hours with continuous shaking prior sampling ininto the GPC instrument.

Melt Flow Rate (MFR)

The melt flow rates are measured with a load of 2.16 kg (MFR₂) at 230°C. The melt flow rate is that quantity of polymer in grams which thetest apparatus standardised to ISO 1133 extrudes within 10 minutes at atemperature of 230° C. under a load of 2.16 kg.

Calculation of Melt Flow Rate MFR₂ (230° C.) of the Propylene Copolymer(B)

${{MFR}(B)} = 10^{\lbrack\frac{{\log{({{MFR}{(P)}})}} - {{w{(A)}} \times {\log{({{MFR}{(A)}})}}}}{w{(B)}}\rbrack}$wherein

-   w(A) is the weight fraction of the polypropylene (A),-   w(B) is the weight fraction of the propylene copolymer (B),-   MFR(A) is the melt flow rate MFR₂ (230° C.) [in g/10 min] measured    according ISO 1133 of the polypropylene (A),-   MFR(P) is the melt flow rate MFR₂ (230° C.) [in g/10 min] measured    according ISO 1133 of the propylene copolymer composition (P),-   MFR(B) is the calculated melt flow rate MFR₂ (230° C.) [in g/10 min]    of the propylene copolymer (B).

Xylene Cold Soluble Fraction (XCS wt %)

Content of xylene cold solubles (XCS) is determined at 25° C. accordingISO 16152; first edition; 2005 Jul. 1.

Hexane Solubles FDA Section 177.1520

1 g of a polymer film of 100 μm thickness is added to 400 ml hexane at50° C. for 2 hours while stirring with a reflux cooler.

After 2 hours the mixture is immediately filtered on a filter paper No41.

The precipitate is collected in an aluminium recipient and the residualhexane is evaporated on a steam bath under N₂ flow.

The amount of hexane solubles is determined by the formula((wt. sample+wt. crucible)−(wt crucible))/(wt. sample)·100.

Melting temperature T_(m), crystallization temperature T_(c) is measuredwith Mettler TA820 differential scanning calorimetry (DSC) on 5-10 mgsamples. Both crystallization and melting curves were obtained during10° C./min cooling and heating scans between 30° C. and 225° C. Meltingand crystallization temperatures were taken as the peaks of endothermsand exotherms.

Also the melt- and crystallization enthalpy (Hm and Hc) were measured bythe DSC method according to ISO 11357-3.

Porosity: BET with N₂ gas, ASTM 4641, apparatus Micromeritics Tristar3000; sample preparation: at a temperature of 50° C., 6 hours in vacuum.

Surface area: BET with N₂ gas ASTM D 3663, apparatus MicromeriticsTristar 3000: sample preparation at a temperature of 50° C., 6 hours invacuum.

Mean particle size is measured with Coulter Counter LS200 at roomtemperature with n-heptane as medium; particle sizes below 100 nm bytransmission electron microscopy.

Sealing Initiation Temperature (SIT); Sealing End Temperature (SET),Sealing Range

The method determines the sealing temperature range (sealing range) ofpolypropylene films. The sealing temperature range is the temperaturerange, in which the films can be sealed according to conditions givenbelow.

The lower limit (heat sealing initiation temperature (SIT)) is thesealing temperature at which a sealing strength of >1 N is achieved. Theupper limit (sealing end temperature (SET)) is reached, when the filmsstick to the sealing device.

The sealing range is determined on a DTC Hot tack tester Model 52-F/201with a film of 25 μm thickness with the following further parameters:

-   Specimen width: 25 mm-   Seal Pressure: 0.66 N/mm²-   Seal Time: 1 sec-   Cool time: 30 sec-   Peel Speed: 42 mm/sec-   Start temperature: 80° C.-   End temperature: 150° C.

Specimen is sealed sealing layer (SL) to sealing layer (SL) at eachsealbar temperature and seal strength (force) is determined at eachstep. All values of the SIT and SET were measured on the multi-layerfilm, like the three layer film as used in the examples. In cases wherethe SIT and SET refer to the propylene copolymer composition (P) or thesealing layer (SL) as such the SIT and SET were measured on a monolayercast film of the propylene copolymer composition (P) and the sealinglayer (SL), respectively, having a thickness of 100 μm as described inapplication No. 10 160 631.7. and application No. 10 160 611.9.

Hot Tack Force

The hot tack force is determined on a DTC Hot tack tester Model 52-F/201with a film of 25 μm thickness with the following further parameters:

-   Specimen width: 25 mm-   Seal Pressure: 1.2 N/mm²-   Seal Time: 0.5 sec-   Cool time: 0.2 sec-   Peel Speed: 200 mm/sec-   Start temperature: 90° C.-   End temperature: 140° C.

The maximum hot tack force, i.e the maximum of a force/temperaturediagram is determined and reported.

Hot tack initiation temperature: is determined from the hot tack curveat the point where the force exceeds 1 N

Gloss was determined on the multi-layerd films according to DIN 67530 atan angle of 20° C.

Transparency, haze and clarity were determined on the multi-layerd filmsaccording to ASTM D 1003-00.

B. Examples

The propylene copolymer compositions (P) of table 1 have been producedin a Borstar PP pilot plant in a two-step polymerization processstarting in a bulk-phase loop reactor followed by polymerization in agas phase reactor, varying the molecular weight as well as hexenecontent by appropriate hydrogen and comonomer feeds. The catalyst usedin the polymerization process was a metallocene catalyst as described inexample 10 of WO 2010/052263 A1.

TABLE 1 Preparation of the propylene copolymer composition (P) P1 P2 P3Loop MFR₂ [g/10 4.0 4.3 4.1 min] C6 [wt.-%] 1.2 0.0 3.5 XCS [wt.-%] <1.5<1.5 <1.5 GPR C6 [wt.-%] 7.4 5.8 6.6 Split [%] 45/55 34/66 58/42Loop/GPR FINAL C6 [wt.-%] 4.8 3.8 5.3 XCS [wt.-%] 15.4 1.9 11.0 HHS[wt.-%] 0.9 0.8 1.0 MFR₂ [g/10 7.9 10.0 11.0 min] Mw [kg/mol] 210 211 nmMWD [—] 2.9 3.0 nm SIT [° C.] 102 108 98 Tm [° C.] 141 149 126 Tc [° C.]100.4 101.2 90.9 Loop defines the polypropylene (A) GPR defines thepropylene copolymer (B) Final defines the propylene copolymer (P) C6 is1-hexene content HHS hexane hot solubles nm not measured SIT Sealing asinitiation temperature measured on a monolayer film [100 μm] asdescribed in application No. 10 160 631.7. and application No. 10 160611.9 P4 is the commercial propylene-ethylene-1-butene terpolymerTD215BF of Borealis AG having a melt flow rate MFR₂ (230° C.) of 6 g/10min, a melting temperature Tm of 130° C.. P5 is the commercialpropylene-ethylene-1-butene terpolymer TD220BF of Borealis AG having amelt flow rate MFR₂ (230° C.) of 6 g/10 min, a melting temperature Tm of132° C.. P6 is the commercial random ethylene-propylene copolymerRE239CF of Borealis AG having a melt flow rate MFR₂ (230° C.) of 11 g/10min, a melting temperature Tm of 140° C.. H-PP is the commercialpolypropylene homopolymer HD234CF of Borealis AG having a melt flow rateMFR₂ (230° C.) of 8 g/10 min, a melting temperature Tm of 162 ° C..

Three layer films were produced at three layer coex line, the filmstructure was OL-CL-SL with a core layer of 33 μm (CL) and an outerlayer of 8.5 μm (OL) and one sealing layer (SL) of 8.5 μm. For the corelayer (CL) and the outer layer (OL) H-PP has been used, whereas for thesealing layer (SL) one of the polymers P1 to P6 have been used. The melttemperature of the polymers was in the range of 247° C. to 252° C. inthe extruder die. The throughput for all three layer was in sum 60 kg/h.The take of speed of the film was 27.5 m/min to 31 m/min as a film widthof 60 cm. The temperature of the chill roll was in the range of 13° C.to 20° C. The temperature of the water bath was in the range of 15° C.to 20° C.

TABLE 2 Properties of the multi-layer polymer film CE1 CE2 CE3 IE1 IE2IE3 P4 P5 P6 P1 P2 P3 SIT [° C.] 105 106 112 104 107 99 SET [° C.] 140140 140 140 140 140 SET − SIT [° C.] 35 34 28 36 33 41 HTF [N] 7.4 6.9 75.9 4.7 7.3 ST [° C.] 115 120 135 120 110 115 T [%] 93.7 93.7 93.6 93.793.7 93.7 H [%] 1.7 2.2 2.6 1.6 1.9 1.6 C [%] 96.7 96.4 95.9 97.2 97.197 TH [μM] 49 50 50 50 51 50 G [%] 139.9 139.8 135.6 142 141.5 142.9 SITis the heat sealing initiation temperature SET is the heat sealing endtemperature SET − SIT is the difference of SET and SIT ST is the sealingtemperature HTF is the hot tack force T Transparancy H Haze C Clarity THThickness G Gloss 20°

The invention claimed is:
 1. Process for producing a multi-layer polymerfilm comprising: providing a core layer (CL) selected from the groupconsisting of polyvinyl alcohols, polyacrylates, polyamides,poly(ethylene terephthalate), polyolefins (PO) and mixtures thereof, asealing layer (SL), and optionally an outer (OL), a further sealinglayer (SL) or a metal layer (ML) wherein: (a) the core layer (CL); (a1)is coated on the one side with a propylene copolymer composition (P)obtaining a sealing layer (SL); and (a2) optionally; (a2-i) is on theother side coated with a polyolefin (PO) obtaining an outer layer (OL);or (a2-ii) is on the other side coated with a propylene copolymercomposition (P) obtaining a second sealing layer (SL); or (a2-iii) is onthe other side metallized obtaining a metal layer (ML), wherein; (b)said propylene copolymer composition (P); (b1) has a comonomer contentin the range of 3.0 to 8.0 wt. %, the comonomer is C₆ α-olefin, (b2)comprises a polypropylene (A) and a polypropylene (B) in the weightratio [(A)/(B)] of 35/65 to 50/50, wherein said polypropylene (A) is apropylene homopolymer (H-A) or a propylene copolymer (C-A) having acomonomer content of below 4.0 wt. %, the comonomers are C₅ to C₁₂α-olefins, and said propylene copolymer (B) has a comonomer content of4.0 to 20.0 wt. %, the comonomer is C₆ α-olefin, and (b3) fulfills theratio MFR (A)/MFR (P)<1.0 wherein MFR(A) is the melt flow rate MFR₂(230° C.) [g/10 min] measured according to ISO 1133 of the polypropylene(A), MFR(P) is the melt flow rate MFR₂ (230° C.) [g/10 min] measuredaccording to ISO 1133 of the propylene copolymer composition (P), and(b4) has a xylene soluble content (XCS) determined at 25° C. accordingto ISO 16152 of below 16.0 wt. %; (b5) a melting temperature Tmdetermined by differential scanning calorimetry (DSC) of at least 135°C., and (b6) a heat sealing temperature (SIT) of equal or below 115° C.,and (b7) is free of any elastomeric polymer component, and wherein themultilayer polymer film is cast and not subjected to a stretching step.2. Process according to claim 1, wherein polymer layers of themultilayer polymer film are coextruded on a cast film line.
 3. Processaccording to claim 1, wherein the propylene copolymer composition (P)and/or the polyolefin (PO) has/have (a) a core layer (CL) being selectedfrom the group consisting of polyvinyl alcohols, polyacrylates,polyamides, poly(ethylene terephthalate), polyolefins (PO) and mixturesthereof, and (b) a sealing layer (SL), said sealing layer (SL) comprisesa propylene copolymer composition (P), said propylene copolymercomposition (P).
 4. Process according to claim 2, wherein moltenpolymers are extruded through slot extrusion dies onto a chill roll tocool the polymers to a solid cast film of at least two layers. 5.Process according to claim 2, wherein melts for the core layer (CL) andthe propylene copolymer composition (P) for the sealing layer (SL) arecoextruded through flat-film multilayer die, and taken off the resultantmulti-layer polymer film over one or more rolls for solidification. 6.Process according to claim 2, wherein melts for the core layer (CL), thepropylene copolymer composition (P) for the sealing layer (SL) and thepolymer for the outer layer (OL) are coextruded through flat-filmmultilayer die, and taken off the resultant multi-layer polymer filmover one or more rolls for solidification.
 7. Process according to claim2, wherein melts for the core layer (CL), the propylene copolymercomposition (P) for the sealing layer (SL) and the polymer for a furthersealing layer (SL) are coextruded through flat-film multilayer die, andtaken off the resultant multi-layer polymer film over one or more rollsfor solidification.
 8. Process according to claim 5, wherein thetake-off roll or the rolls, by means of which the extruded film iscooled and solidified, are kept at a temperature from 10 to 50° C. 9.Process according to claim 5, wherein the take-off roll or the rolls, bymeans of which the extruded film is cooled and solidified, are kept at atemperature from 15 to 40° C.
 10. Process according to claim 5, whereinthe take-off roll or the rolls, by means of which the extruded film iscooled and solidified, are kept at a temperature from 10 to 50° C. 11.Process according to claim 1, wherein the multi-layer film iscorona-treated or flame-treated.
 12. Process according to claim 11,wherein the corona treatment or flame treatment is carried out bypassing the film between two conductor elements serving as electrodeswith high voltage.
 13. Process according to claim 12, wherein the highvoltage is an alternating voltage.